Code division multiple access (CDMA) is a digital wireless technology that inherently has relatively greater bandwidth capacity, i.e., that inherently permits the servicing of more telephone calls per frequency band, than other wireless communication technologies. Moreover, the spread spectrum principles of CDMA inherently provide secure communications. U.S. Pat. No. 4,901,307, incorporated herein by reference, sets forth details of a CDMA system, which can be used to transmit both voice calls and non-voice computer data.
Despite the advantages of CDMA, other wireless systems exist that use other principles. For example, in much of the world GSM is used, which employs a version of time division multiple access.
Whether CDMA principles or other wireless principles are used, wireless communication systems can be thought of as having two main components, namely, the wireless radio access network (RAN) and the core infrastructure which communicates with the RAN and with external systems, such as the public switched telephone network (PSTN), the Internet (particularly although not exclusively for data calls), etc. The core infrastructures associated with the various wireless technologies can be very expensive, both in terms of hardware and in terms of developing communication protocols to support particularized, typically system-specific call switching, subscription and attendant authentication and call monitoring, and billing. Consequently, the communication protocols of one wireless system (in the case of GSM, GSM protocols, and in the case of CDMA such as cdma2000-1x, IS-41 protocols) may not be compatible with those of another system without expensively prohibitive alterations in the core infrastructure of one system or the other.
From the disclosure above, the present invention recognizes that it would be desirable to enable the use of a CDMA-based RAN, with its attendant advantages, not only with a CDMA core infrastructure but also with a GSM-based core infrastructure, because GSM is extant in much of the world. The present invention still further recognizes, in light of the above, the desirability of minimizing if not eliminating the need to modify the communication protocols of the GSM core infrastructure.
Still further, the present invention recognizes that a dual-mode mobile station that advantageously interfaces with a CDMA RAN might be provided to use a GSM core infrastructure when in, e.g., Europe, and to use a CDMA infrastructure while in, e.g., the United States. Unfortunately, heretofore such a mobile station would require a subscription and telephone number in the GSM system and a separate subscription and telephone number in the CDMA system. This increases both complexity and cost from a user's standpoint. The present invention recognizes that it would be desirable to permit use of a dual-mode CDMA mobile station without requiring a subscription in both a CDMA core and a GSM core.